 On December 21, 2001, a version incorporating support for SpamAssassin was released, making MIMEDefang a filter for both spam and viruses.Skoll's company, Roaring Penguin Software, currently markets a commercial anti-spam product known as CanIt, which is based on the open-source version of MIMEDefang.The Milter library included with Sendmail uses POSIX threads to allow multiple concurrent filters.